The present invention relates to the field of fluid handling and control; particularly, to a passive multi-channel valve capable of completely purging a terminal channel.
Those in the fluid handling industry have long-recognized the need for systems capable of delivering two or more fluids from respective reservoirs while preventing contaminants from entering the reservoirs, and systems that facilitate purging of critical fluid delivery channels. However, these desired characteristics have not previously been incorporated into a single valve.
The fluid handling industry has long-recognized the value in the simplicity of passive valves. Examples of such valves include U.S. Pat. No. 4,846,810 to Gerber, U.S. Pat. No. 5,080,138 to Haviv, and U.S. Pat. No. 5,836,484 to Gerber. In their most general sense, the valves of the ""810, ""138, and ""484 patents incorporate an elastomeric sheath that tightly fits onto a valve body and controls the delivery of the fluid. Fluid is delivered through a channel in the valve body to a point in which the channel terminates against the inside surface of the annular sheath. Upon, a rise in fluid pressure above a predetermined level, known as the cracking pressure, the fluid forces the elastomeric sheath away from the valve body, thereby allowing the fluid to create a chamber between the sheath and the body into which it can flow. In the ""810 and ""138 devices, as the chamber expands due to the ingress of the pressurized fluid, the sheath is forced away from the body in the vicinity of a discharge channel, or channels, thereby permitting the fluid to exit the chamber through the discharge channel. As the fluid pressure falls below the cracking pressure, the sheath returns to a normal position tightly against the body, thereby sealing off the delivery channel and forcing the fluid remaining in the chamber into the discharge channel. The mechanism is similar in the ""484 device, except that the elastic rebound of the sheath, instead of forcing fluid into a discharge channel, forces the fluid from the chamber to atmosphere.
The elastomeric sheaths of the ""810, ""138, and ""484 valves function quite well in preventing contamination via backflow and migration of contaminants with a single fluid source. However, these do not satisfy the demand for a passive valve that can be effectively purged and can handle multiple fluids, and the unique challenges associated with multiple fluid control. In fact, the handling of multiple fluids and the associated challenges is often as important, if not more important, than the prevention of backflow.
Addressing the purge function, the prior art devices all lack a true purging capacity. In the ""810, ""138, and ""410 devices, the elastic rebound of the sheath tends to force the fluid out of the chamber created by the distention of the elastomeric sheath, and into either a discharge channel or to atmosphere, as described above. At no point is the discharge channel or atmospheric chamber completely purged of fluid. In this sense, the prior devices might be most accurately seen to have a xe2x80x9cvolume reducingxe2x80x9d capacity, in that the closing action of these valves does not truly purge but does tend to reduce the amount of fluid remaining in the valve when the fluid pressure drops below the predetermined cracking pressure.
To consider the practical aspects of this problem from a more concrete perspective, by way of illustration and not limitation, consider an application requiring the management of two fluids, one a fluid that for some reason is best handled by completely expelling it from the valve after closing, another a fluid that may remain in the valve after closing. By adjusting aspects of the design as will be discussed in detail below, possibly including the relative volumes of the respective fluid chambers, the valve of the instant design can be made to purge the first fluid from the valve. In such an exemplary construction, the second fluid may flow sequentially or for a longer time than the first fluid through the discharge channel as the valve is closing, thus purging the discharge channel of the first fluid with the second. A possible application, by way of example and not limitation, might be the provision of a heparin flush following the infusion of another pharmaceutical ingredient, to discourage in vivo clotting at the delivery point of the infusion.
An additional problem not addressed in the prior art relates to the problem of diffusion of small molecules through the elastomeric sheath. Numerous prior art valves are exposed in large part to the atmosphere, unless they were to be enclosed in a separate and specially designed chamber. Exposure to atmosphere would allow the continuous escape of small molecules through the elastomeric sheath in response to the concentration gradient present between the fluid in the valve and the atmosphere. Such diffusion would tend to increase the concentration of those elements of the fluid which are unable to move across the elastomeric sheath. To utilize a concrete example, by way of example and not limitation, if an active ingredient with a relatively large chemical structure were dissolved in ethanol, which has a very small chemical structure, ethanol molecules would tend to migrate across the elastomeric sheath to the atmosphere, thereby increasing the relative concentration in the fluid of the large molecules that were unable to diffuse across the barrier. If these large molecules were a drug with critical concentration dispensing requirements, it could pose adverse medical effects. Therefore, minimum exposure to the atmosphere is highly desirable.
Since the instant invention has a relatively small area of exposure to atmosphere, in certain embodiments, it may obviate a great deal of this problem. Any diffusion that should occur across a first elastomeric sheath diffusion area occurs into a closed space, and must then diffuse through a second portion of elastomeric sheath, generally having a smaller area for diffusion than the first diffusion area, in order to escape to atmosphere. This double barrier diffusion path may act to slow diffusion.
Perhaps most importantly, unlike the prior art designs, the present invention adds the capacity to effectively mix two or more fluids. Most obviously, a multiple chamber valve has the capacity to dispense multiple components at the same time in a mixed dispensing action, but the instant invention also adds considerably more than mixing to the fluid management capacity of the art.
For example, the traditional means of regulating the cracking pressure of the valve""s elastomeric sheath, as seen in the prior art devices noted above, is by varying the thickness of the sheath and the bulk modulus of the elastomeric material. The instant invention, as will be described in detail below, adds new methods for regulating the cracking pressure of the valve, as well as tuning the cracking pressure at various locations on the sheath. By way of example, and not limitation, the cracking pressure can be regulated by varying the location of divisions of the chambers in a generally circumferential manner, or by varying the size of the divisions giving one chamber a larger arc of the elastomeric sheath than that of the other, or others. Such an increase would effectively create one chamber exposed to a longer spring with the same spring constant as the other, thus creating a lower cracking pressure.
As an additional fluid management tool, the instant invention, as will be described in detail below, offers the capacity for enhanced features to prevent fluid backflow. By way of example, and not limitation, the valve can be constructed with fluid entrance and exit ports of differing sizes and geometries. For example, a first port that supplies fluid to a chamber requires a first cracking pressure to force the seal from the opening. Fluid may then exit the chamber from a second port. If reverse flow tried to enter the chamber via the second port and the second port was one half the area of the first port, then the second (backflow) cracking pressure would be twice that of the first (forward flow) cracking pressure.
In contrast to valves seen in the prior art, the instant invention could also, by way of example and not limitation, be constructed so that the elastomeric sheath had areas of different thickness occluding the entrance and exit ports. A thicker sheath area over the exit port relative to the thickness seen over the entrance port would tend to require a second cracking pressure greater than the first cracking pressure.
Similarly, as will be discussed in detail below, and by way of example and not limitation, be present invention may be constructed with a second elastomeric sheath covering only the area of the discharge port. Such a construction would exert a check valve effect over the discharge port and would tend to substantially prevent backflow.
Accordingly, the art has needed a low cost, multi-channel passive valve that effectively prevents contamination of the fluid sources, allows for the purging of critical fluid delivery channels while accounting for the unique properties of the fluids being delivered, and gives enhanced abilities to manage fluid delivery characteristics. While some of the prior art devices attempted to improve the state of the art of single-channel non-purging valves, none have achieved the beneficial attributes of the present invention. With these capabilities taken into consideration, the instant invention addresses many of the shortcomings of the prior art and offers significant benefits heretofore unavailable. Further, none of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.
In its most general configuration, the present invention advances the state of the art with a variety of new capabilities and overcomes many of the shortcomings and limitations of prior devices in new and novel ways, and in any of a number of generally effective configurations. In one of the many preferable configurations, the multi-channel valve apparatus incorporates a valve seat, a valve seal, and valve housing, among other features. The valve is entirely passive in operation. The apparatus is generally configured such that the valve seal tightly encloses at least a portion of the valve seat and the valve housing releasably secures the valve seal to the valve seat. The apparatus is highly scalable in size and adaptable to a wide variety of fluids.
The valve seat is formed to have a plurality of channels directing the flow of at least one fluid, with at least one of the plurality of channels being at least one cross chamber channel. The number of channels present in a particular embodiment may reflect particular handling characteristics of the fluids to be utilized, or manufacturing considerations in the fabrication of the apparatus.
The valve seal tightly encloses a portion of the valve seat thereby covering a plurality of inlet and exit openings. In a basic configuration, the valve seal is formed to create a plurality of chambers when distended from the valve seat by a fluid at a predetermined pressure.
In an exemplary embodiment, the plurality of channels includes a plurality of inlet channels, at least one terminal channel, and at least one cross chamber channel connecting the plurality of chambers. Additionally, the valve seat is formed to have a seal engagement shelf, a top surface, and an exit surface.
A first inlet opening and a second inlet opening may be located on the top surface of the valve seat and a terminal channel exit opening may be located on the exit surface of the valve seat. In one particular embodiment all other channel openings, including a first exit opening, second exit opening, cross chamber inlet opening, cross chamber exit opening, and terminal channel inlet opening, are located on a sidewall of the valve seat.
The valve seal may be formed to have a plurality of separators, each having a separator width, a plurality of elastomeric portions each having an elastomeric portion thickness, and a plurality of retainers. Additionally, the exemplary valve seal incorporates a first elastomeric portion having a first thickness and a second elastomeric portion having a second thickness. The first elastomeric portion releasably covers the first exit opening and the cross chamber channel inlet opening, whereas the second elastomeric portion releasably covers the second exit opening, and the terminal channel inlet opening, thus creating two chambers. In additional variations the second elastomeric portion may releasably cover the cross chamber exit opening.
The valve housing may be formed to have an interior surface, an exterior surface, and a seal engagement ledge. The valve seal tightly mounts over the valve seat with a seat engagement ledge cooperating with the seal engagement shelf. The valve housing then fits over the valve seal and the valve seat releasably retains the valve seal through the cooperation of a seal engagement ledge and a retainer engagement shelf. Additionally, the inner surface of the valve housing may compress portions of a distal retainer and a proximal retainer formed in the valve seal to assist in forming a fluid-tight connection between the valve seal and the valve seat.
The sequence of the valve""s operation begins with pressurized inflow through the plurality of inlet channels. When the cracking pressure of the valve has been reached, the pressure of the inflowing fluid distends the elastomeric portions of the valve seal, filling the chambers. The valve seal may be configured so that different chambers may have different cracking pressures. When the inflow pressure drops, the elastomeric portions of the seal force fluid through the terminal channel and out of the valve. The flow of a plurality of pressurized fluids may be staged sequentially or may flow simultaneously.
A unidirectional flow control device may be added in the cross chamber channel to prevent a second chamber fluid from entering the cross chamber channel exit opening. Flow may be configured so as to purge the entire terminal channel ensuring that all of the second chamber fluid is discharged from the terminal channel.
The plurality of chambers may include numerous variations resulting in embodiments that may be useful in a wide variety of industries. One such variation includes chambers having substantially equal volumes or substantially unequal volumes.
Varying the volumes of the plurality of chambers may be accomplished in a number of ways. For example, the locations of separators may be varied so that their locations are not substantially opposite each other. Separator width may be varied to be substantially equal or substantially unequal, thereby changing the characteristics of the chambers. Additionally, the properties of different elastomeric portions of the valve seal may be varied. For example, the bulk modulus of the valve seal may be varied in different portions of the valve seal, thereby influencing the volume, as well as the cracking pressure, of the chambers. In yet another variation, the thickness of different portions of the valve seal may be varied to produce desired effects, including varying the thickness of the elastomeric portions in strategic locations in the vicinity of the openings, so as to create directed channels within the chambers.
Another variation of the apparatus includes a backflow prevention secondary elastomeric member adapted to tightly fit in a secondary recess formed in the valve seat and situated to cover the exit openings. The valve seal may then cover the valve seat and secondary elastomeric member as previously described. The extra backflow protection is provided by the fact that if pressurized fluid were to enter the terminal channel, distending the second chamber and beginning to flow through the cross chamber channel to distend the first chamber, the fluid would act against the seal side of the secondary elastomeric member, thereby creating a tighter closure between the secondary elastomeric member and the inlet channel exit openings.
Additional variations of the apparatus incorporate valve housing alterations. In certain applications, such as those attempting to minimize the possibilities for diffusion across the elastomeric valve seal, it is advantageous to minimize the seal area that is exposed to atmosphere. Alternatively, certain applications warrant the additional backflow protection offered by having the valve housing vented to atmosphere.
Additional backflow prevention may be further obtained by varying the actual size of the various inlet and exit openings. For example, a small terminal channel inlet opening would require a tremendous backpressure to achieve the force necessary to distend the second chamber.
The plurality of channels may be formed to facilitate the specific fluid flow parameters of any particular application. For example, the plurality of channels may be extremely smooth and straight for optimum flow and minimum resistance, or they may be formed with harsh angles allowing for ease in manufacture. Additionally, the channels may be formed to take any shape and may be lined to prevent corrosion and reduce resistance. Similarly, the plurality of inlet openings may be adapted to mate with any fluid handling adaptor or fitting.
An alternative chamber forming method may include the cooperation of the valve seat and the valve housing to bound a plurality of elastomeric portions, thereby creating a plurality of chambers. For instance, in one embodiment the valve seat may be formed with a plurality of recesses in which a matching plurality of cooperating ledges on the inner surface of the valve housing tightly fit, compressing the valve seal. In this particular example, the cooperating recesses and ledges act to perform the same function as the plurality of separators previously described.
These variations, modifications, alternatives, and alterations of the various preferred embodiments, arrangements, and configurations may be used alone or in combination with one another as will become more readily apparent to those with skill in the art with reference to the following detailed description of the preferred embodiments and the accompanying figures and drawings.